1. Field of Invention
The disclosure relates to an output amplifier. More particularly, the disclosure relates to an output amplifier of a source driver.
2. Description of Related Art
In an electronic circuit, an output amplifier transmits signals to a terminal and to drive the next stage of the circuit. For example, in a liquid crystal display, a source driver employs an output amplifier to apply a voltage required for the display panel. The output amplifier, therefore, is an essential device in the source driver.
As the size and the frame rate of the display panel increases, the output amplifier, including a previous stage and an output stage, needs to react more quickly, and also needs to reduce the power consumption. For example, when the frame rate increases, the output buffer of the source driver needs to charge the pixel voltage to a target value within a short time, hence the transistor size of the output amplifier needs to be increased, and the static current or leakage current becomes large as a result.
In addition, because the transistor size of the output amplifier is increased, the loading seen by the stage prior to the output amplifier is increased accordingly, and the stage prior to the output amplifier cannot drive the output amplifier effectively, which reduces the operation speed of the whole source driver.
For the forgoing reasons, there is a need for a new output amplifier to reduce the static current and to improve the operation speed thereof.